Process for manufacturing alcohols by oxidation of hydrocarbons

ABSTRACT

A process for manufacturing alcohols by oxidation of saturated hydrocarbons containing five-eight carbon atoms per molecule, in the liquid phase, by means of molecular oxygen, in the presence of a boron compound, wherein the oxidation product is successively hydrolyzed, saponified and distilled, said process comprising vaporizing a part of the unconverted hydrocarbon contained in the said oxidation product, before saponification, and thereafter treating the vaporized hydrocarbon by means of mineral base and finally recycling said hydrocarbon to the oxidation zone.

United States Patent Alagy et al.

[54] PROCESS FOR MANUFACTURING ALCOHOLS BY OXIDATION OF HYDROCARBONS Inventors: Jacob Alagy, La Celle St Cloud; Francois Bigache; Bernard Cha, both of Chatou, all of France Institut Francais Du Petrole Carburants Et Lubrifiants, Rueil Malmaison I-lauts de Seine, France Filed: May 14, 1968 Appl. No.: 729,035

[73] Assignee:

[30] Foreign Application Priority Data May 29, 1967 France ..67108317 US. Cl. ..260/63l B, 260/462 A, 260/586 B, 260/597 R, 260/617 H, 260/639 B Int. Cl. ..C07c 35/08, C07c 31/02 Field ofSearch ..260/63l P, 632 C, 632 CB, 643 E, 260/612 H, 639 B, 586 8,462 A References Cited UNITED STATES PATENTS 5/ 1952 Carlson et al. ..260/643 E 5/1952 Hale et al. ..260/643 E X 1/1953 Smith ..260/643 E SOLU AQUEOUS WATER PHASE ALKALINE HON [151 3,683,035 51 Aug. 8, 1972 3,359,335 12/1967 Roming ..260/643 E 3,439,041 4/1969 Gey et a1. ..260/631 13 X 2,557,281 6/1951 Hamblet et a1 ..260/631 B 3,232,704 2/ 1966 Helbig et al. ..260/63l B 3,287,423 11/1966 Steeman et al ..260/631 B 3,442,959 5/ 1969 Sujerman ..260/631 B FOREIGN PATENTS OR APPLICATIONS 900,627 7/1962 Great Britain ..260/643 E Primary Examiner-Leon Zitver Assistant Examiner-Joseph E. Evans Attorney-Craig, Antonelli, Stewart and Hill [5 7] ABSTRACT 4 Claims, 1 Drawing Figure NAOH SOLUTION PATENTEDAus 8l972 3.633.035

NEUTRALIZATION WASHING coumw COLUMN 6 ORGANIC 1 PHASE GASEOUS v PHASE M1 12 I3 5 OX'DATION VAPORIZATION 1 J QVESSEL SVESSEL AQUEOUS WATER PHASE gougous HA E uucouvamn SO LWON uvoggcmou HYDROLYSIS AND Q' 'F |QU|D WASHiNG VESSEL 8 9 PHASE -7 21 ORGANIC I PHASE ORGANIC 9 PHASE 25 3 ALCOHOL-KETONE MIXTURE 13 I AQUEOUS SOLUTION INVENTORS JpcaE any, flnncu; 816401: a!

BY (4, 9 47m14' ATTORNEYS PROCESS FOR MANUFACTURING ALCOHOLS BY OXIDATION OFHYDROCARBONS It is known to oxidize linear or cyclic saturated hydrocarbons, in a liquid phase, in the presence of a boric acid (for example ortho-, metaor pyroboric acid), boric anhydride or a boric ester, or any other equivalent boron compound, to obtain boric esters of the alcohols corresponding to said hydrocarbons.

Oxygen is usually employed in a concentration of l to 25 percent as a mixture with an inert gas such as nitrogen.

For example, the oxidation of cyclohexane, in these conditions, provides for a cyclohexyl borate. Other oxidizable hydrocarbons are those which contain from five to eight carbon atoms per molecule, for example hexane, heptane, octane, isooctane, cycloheptane, cyclooctane, methylcyclohexane and dimethylcyclohexanes (ortho-, metaor para-).

The oxidation temperature is usually between 100 and 220 C., preferably between 140 and 190 C., with a pressure which is sufficient to maintain a liquid phase, for example between 1 and 40 atmospheres.

By hydrolysis of the reaction product, before or after a part or the whole of the non-converted hydrocarbon has been separated, boric acid may be recovered either directly in the solid state or as an aqueous solution which may be subjected to crystallization as well as an organic phase which contains the expected alcohol, usually together with a minor proportion of the corresponding ketone.

As hydrolysis agent, water or the mother-waters of a prior crystallization of boric acid may be used. The amount of water must be at least the stoichiometrical amount with respect to the hydrolysis reaction; usually 0.1 to 2 parts by volume of aqueous phase may be used for one part by volume of effluent from the oxidation zone, and the temperature is most often between 20 and 170 C. t

The recovered boric acid may be re-used in another oxidation operation, preferably after dehydration.

The unconverted hydrocarbon may be recycled. lts recovery may be carried out by distillation of the organic phase after hydrolysis and saponification.

Preferably this distillation will be preceded by a partial distillation of the hydrocarbon (for example to 90 percent of the present hydrocarbon) by release of pressure on the liquid efiluent from the oxidation zone, before saponification and preferably also before hydrolysis. The thus obtained vapor phase, after condensation', will be sent back to the oxidation reactors, whereas the liquid phase will be subjected to hydroly sis, saponification and distillation.

Since this operation may be carried out continuously, just as described above, a substantial lowering in the conversion of the hydrocarbon may be observed after some time.

The object of this invention is to avoid the said inconvenience. It has been observed that a washing of the hydrocarbon contained in the vapors obtained during the release of pressure was necessary, said washing being carried out with a mineral base such as an oxide, a hydroxide or a carbonate of an alkali or alkali-earth metal, for example sodium hydroxide, ammonia, sodium carbonate, potassium carbonate, potassium hydroxide or calcium hydroxide, and followed by a washing with water. It appears that formic acid or any other light product separated during the release of pressure, if it is not rejected, results into a partial inhibition of the reaction.

Advantageously there will be used as neutralizing medium, the excess of sodium hydroxide contained in the aqueous phase separated from the saponified liquid phase issuing from the release unit. This basic solution contains oxidation products of value, for example cyclohexanol and cyclohexanone, and the organic liquid phase newly extracts these products which otherwise would be lost, thus resulting into a substantial yield loss in the unit.

The amount of mineral base will be advantageously at least that amount which would correspond to the neutralization of 50 percent of the acids present.

However this base is preferably used in an amount corresponding to 110-300 percent of the theoretical amount corresponding to the neutralization of the acids, in order to realize simultaneously a saponification of the esters present. It is of little importance that this base be in the form of a concentrated or diluted aqueous solution.

The joint drawing is given by way of illustration of an embodiment of this invention.

The liquid effluent from the last oxidation vessel (or from the sole oxidation vessel) 1, which is withdrawn through pipe 10, after cooling in the heat exchanger 2, is admitted into the vaporization vessel 3. With hydrocarbons containing five-eight carbon atoms this vaporization may be carried out, for example at 180 C. preferably l40 C. under a pressure of 2-8 kg/cm preferably 3-? kglcm The gaseous phase which is withdrawn through pipe 11 and condensed in the heat exchanger 4, is admixed in the neutralization column 5, with an alkaline solution from pipe 12. The aqueous phase is withdrawn from the column through pipe 13, and the organic phase through pipe 14. The latter is admixed with water issuing from pipe 15 and introduced into the washing column 6. The aqueous phase is withdrawn through pipe 16 and the organic phase through pipe 17. This phase which consists essentially of unconverted hydrocarbon, is sent back to the oxidation step. The liquid phase from the vaporization vessel 3 is withdrawn through pipe 18, is subjected to the usual treatment, i.e., hydrolysis and washing in the vessel 7 by means of an aqueous solution of boric acid or water, or a mixture of both, fed through pipe 19.

The aqueous phase which contains water-soluble components is sent through pipe 20 to the step wherein boric acid is recovered. The organic phase is withdrawn through pipe 21 and saponified in vessel 8, the sodium hydroxide solution being fed through pipe 22 and diluted with the aqueous phase of pipe 16, issuing from the washing step of column 6.

The residual alkaline aqueous phase is withdrawn through pipe 12 and used to feed the neutralization column 5. The organic phase, which contains the oxidation products and a part of the unconverted hydrocarbon, is sent through pipe 23 to the separation step 9, for example by distillation, where the unconverted hydrocarbon issues through pipe 24 to be sent back to the oxidation step, the alcohol-ketone mixture being extracted through pipe 25.

The following, non-limitative examples 2 and 3 illustrate an embodiment of this invention. Example 1 is given by way of comparison and forms no part of this invention.

EXAMPLE 1 Cyclohexane is oxidized in several successive vessels, in the presence of boric acid, by means of an oxygencontaining gas at 165 C. and about 10 atmospheres.

The liquid phase issuing from the last vessel, which contains the oxidation products as well as the excess of boric acid, is subjected to a release of pressure down to 5 atmospheres at 120 C., the latter temperature being maintained by means of a heat exchanger. The obtained vapor phase contains about 93 percent by weight of cyclohexane. A minor proportion of the oxidation products is carried away about 8 percent by weight of the organic acids (essentially formic acid) which are present in the effluent of the last vessel as well as 10 percent of the cyclohexyl organic esters. The total amount of vapor phase separated during this pressure release amounts to about 35 percent of the total effluent from the reaction vessels. After cooling, the condensate is sent back to the reaction vessels in order to be subjected to another oxidation step.

The aqueous phase from the saponification of the hydrolysis effluent is not used to carry out a neutralization of the condensate and thus is only rejected.

After 7 days of continuous run, the molar yield of cyclohexanol cyclohexanone is 89 percent for a cyclohexane conversion of 8.l percent.

EXAMPLE 2 Example 1 is repeated, except that the condensed hydrocarbon is neutralized by means of a 0.2N sodium hydroxide solution which is used in an amount of 120 percent with respect to the amount corresponding to the theoretical neutralization of the acids, then it is washed with water before being recycled to the oxidation vessels. The aqueous phase issued from the saponification of the hydrolysis effluent is not used, here again, to carry out the neutralization of the condensate. It is only rejected.

The molar yield of cyclohexanol cyclohexanone is 89 percent and the conversion has attained l 1 percent.

EXAMPLE 3 Example 1 is repeated, except that the condensed hydrocarbon is neutralized by means of the aqueous phase issued from the saponification of the hydrolysis efiluent. This aqueous phase contains an excess of sodium hydroxide, which has not been consumed during the saponification, in an amount equal to that defined in Example 2.

Under these conditions, the molar yield of cyclohexanol+cyclohexanone is 91 percent for a conversion rate of 1 1 percent.

We claim:

1. A process for manufacturing alcohols by oxidation of saturated hydrocarbons containing five-eight carbon atoms per molecule, in the liquid phase at a temperature between and 200 C. with a pressure between 1 and 40 atmospheres, with molecular oxygen, in the presence of boron compound selected from the group consisting o orthoboric acid, metaboric acid, pyroboric acid, boric anhydride and a boric ester, wherein the oxidation product is successively hydrolyzed, saponified and distilled, said process comprising vaporizing 10-90 percent of the unconverted hydrocarbon contained in the said oxidation product, before hydrolysis and saponification, and thereafter condensing the vaporized hydrocarbon and treating the condensed hydrocarbon with an amount of a mineral base corresponding to the neutralization of at least 50 percent of the free acids and finally recycling said treated hydrocarbon to the oxidation zone, said mineral base having been used to saponify the oxidation product prior to the treatment of said condensed hydrocarbon. v

2. A process according to claim 1, wherein the mineral base is sodium hydroxide.

3. A process according to claim 1, wherein there is used an excess of mineral base with respect to the free acids.

4. A process according to claim 1, wherein the hydrocarbon is cyclohexane. 

2. A process according to claim 1, wherein the mineral base is sodium hydroxide.
 3. A process according to claim 1, wherein there is used an excess of mineral base with respect to the free acids.
 4. A process according to claim 1, wherein the hydrocarbon is cyclohexane. 